package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;

import java.lang.reflect.*;
import java.util.List;
import java.util.Map;

/**
 * 会话对象sqlSession类定义
 */

public class DefaultSqlSession implements SqlSession {
    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) throws Exception {

        //将要完成对simpleExecutor里的query方法的调用
        simpleExecutor simpleExecutor = new simpleExecutor();
        //MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        Map<String, MappedStatement> mappedStatementMap = configuration.getMappedStatementMap();
        MappedStatement mappedStatement = mappedStatementMap.get(statementId);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);

        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementId, Object... params) throws Exception {
        List<Object> objects = selectList(statementId, params);
        if(objects.size()==1){//只有一条
            return (T) objects.get(0);
        }else{
            throw new RuntimeException("查询记录为空或者返回结果过多！");
        }
    }

    public void addUser(String statementId, Object... params) throws Exception {
        //将要完成对simpleExecutor里的query方法的调用
        simpleExecutor simpleExecutor = new simpleExecutor();
        //MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        Map<String, MappedStatement> mappedStatementMap = configuration.getMappedStatementMap();
        MappedStatement mappedStatement = mappedStatementMap.get(statementId);
        simpleExecutor.add(configuration, mappedStatement, params);
    }

    public void deleteUser(String statementId, Object... params) throws Exception {
        //将要完成对simpleExecutor里的query方法的调用
        simpleExecutor simpleExecutor = new simpleExecutor();
        //MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        Map<String, MappedStatement> mappedStatementMap = configuration.getMappedStatementMap();
        MappedStatement mappedStatement = mappedStatementMap.get(statementId);
        simpleExecutor.delete(configuration, mappedStatement, params);
    }

    public void updateUser(String statementId, Object... params) throws Exception {
        //将要完成对simpleExecutor里的query方法的调用
        simpleExecutor simpleExecutor = new simpleExecutor();
        //MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        Map<String, MappedStatement> mappedStatementMap = configuration.getMappedStatementMap();
        MappedStatement mappedStatement = mappedStatementMap.get(statementId);
        simpleExecutor.update(configuration, mappedStatement, params);
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {

        //使用jdk动态代理，为dao接口生成代理对象并返回
        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            /**
             * @param proxy:是对当前代理对象的引用
             * @param method：当前被调用方法的引用
             * @param args:传递的参数
             */
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                //底层还是执行jdbc，根据不同情况调用selectList，selectOne
                //准备参数 1、statementId：sql语句唯一标识，namespace.id=接口全限定名.方法名

                //方法名：findAll
                String methodName = method.getName();
                //接口全限定名
                String className = method.getDeclaringClass().getName();
                //组装statementId
                String statementId = className+"."+methodName;

                //准备参数2;params:args

                //新增
                if("addUser".equals(methodName)){
                    addUser(statementId, args);
                    return null;
                }
                //删除
                if("deleteUser".equals(methodName)){
                    deleteUser(statementId, args);
                    return null;
                }
                //修改
                if("updateUser".equals(methodName)){
                    updateUser(statementId, args);
                    return null;
                }


                //获取当前被调用方法的返回值类型
                Type genericReturnType = method.getGenericReturnType();
                //判断是否进行了泛型类型类型参数化
                if(genericReturnType instanceof ParameterizedType){
                    List<Object> objects = selectList(statementId, args);
                    return objects;
                }else {
                    Object objects = selectOne(statementId, args);
                    return objects;
                }

            }
        });
        return (T) proxyInstance;
    }
}
